The invention relates to a sterile disposable hemodiafiltration set to be connected to a dialysis machine comprising a dialyzer with an extracorporeal blood path and a dialysis liquid supply line, which can be connected to the dialyzer.
In the conventional hemodialysis treatment impurities are separated from the blood in the dialyzer by diffusion while the separation of impurities in hemodiafiltration treatment is effected both by diffusion and by convection dialysis liquid being supplied as a substitute liquid to the blood in the extracorporeal path. Hemodiafiltration treatment is preferred because also greater molecules are separated from the blood; greater molecules cannot be separated to the same extent when the dialysis treatment includes diffusion only. The dialysis liquid to be supplied to the blood as the substitute liquid is of course subject to higher demands as to sterility than dialysis liquid passing through the dialyzer and, therefore, it undergoes supplementary filtering before being supplied to the blood path.
U.S. Pat. No. 4,702,829 describes a machine for hemodiafiltration wherein the dialysis liquid to be used as substitute liquid is passed through two sterile filters provided in the machine which are not used for filtering the dialysis liquid to be supplied to the dialyzer. Having passed the sterile filters the substitute liquid is passed through a disposable line section including a microfilter and being connected to the blood path either on the outlet side of the dialyzer (post-dilution) or on the inlet side of the dialyzer (pre-dilution).
In the dialysis machine intended for hemodiafiltration according to U.S. Pat. No. 4,702,829 as in other dialysis machines on the market, intended for hemodiafiltration there is provided on the machine a separate outlet for substitute liquid to which a disposable set forming part of the hemodiafiltration circuit is connected in order to set up the dialysis machine for hemodiafiltration treatment, said circuit being partly permanent and exposed to disinfection between the treatments in the dialysis machine especially constructed for hemodiafiltration.